This invention is a marine propeller drive system adaptable to propelling power boats through and over water at high speeds and efficiency, the system being particularly adaptable to propelling high speed planing boats such as catamarans. In propelling a boat forward at high speeds and efficiency it is desirable that its propeller be adjustable in its depth of operation below the water surface as well as with its axis of rotation set at an optimum angle for speed and efficiency.
One marine propulsion system representative of the prior art is one in which a propeller at the end of a long drive shaft is lifted or lowered about a pivot at the stern of the boat. The propeller is lifted up or lowered to change its depth but its angle of operation is correspondingly changed limitedly due to the length of the drive shaft. Such a system is disclosed in U.S. Pat. No. 5,791,954, Johnson, Jr., issued Aug. 11, 1998. Another prior art system of propulsion is one in which the propeller shaft is much shorter and the range of angular orientation of the propeller on its axis of rotation is greater but in orienting the propeller its depth of operation is limited by the orientation. Such a system is disclosed in U.S. Pat. No. 3,933,116, Adams, et. al., issued Jan. 20, 1976. In other words, at one side of the spectrum of systems the depth of operation of the propeller determines its angle of operation whereas on the other side of the spectrum the angle of operation determines the depth of operation.
According to the present invention, the propeller is a marine propulsion system driven by apparatus in which the propeller is adjustable in its depth of operation independently of its angle of operation. This is made possible by supporting the propeller and its propeller shaft and skeg support assembly adjustable about a pivot in an overhanging beam assembly and by providing an intermediate connecting shaft between the engine drive shaft and the propeller shaft. In addition, the level of the overhanging beam assembly with the supporting skeg assembly is vertically adjustable to establish the depth of operation of the propeller below the water level. The details of construction and operation of the assembly will become more apparent upon review of the description of the invention in relation to the drawings accompanying this specification.
A principal object of the present invention is to provide a boat propulsion system in which the angle of the axis of rotation of the propeller and the depth of operation of the propeller can be selected independently of each other and in which the entire assembly can be laterally adjustable to steer the boat.
Another object of the invention is to provide a system of propeller propulsion for a boat to be operated at high speed in which the propeller angle of rotation is adjustable for operation at an ultimate in efficiency.
Still another object of the invention is to provide a boat propulsion system in which the propeller can be operated at any of an infinite number of angles in a given angular range independently of its depth of operation.
Another important and allied objective of the invention is to provide a system in which the propeller operated at a selected angle of operation can be independently raised and lowered to establish an optimum depth of operation.
A principal feature of the invention compared to prior art stem drive systems for water craft is that it allows infinite adjustment of the propeller shaft height and angularity or attitude relative to the running plane of the boat, and additionally that such adjustments can be made while the boat is under way.
Other objects and structural features which are believed to be characteristic of the invention are set forth with particularity in the appended claims. My invention, however, both in organization and manner of construction, together with further objects and features thereof may be best understood by reference to the following description taken in connection with the accompanying drawings.
According to the present invention hereafter described in detail, the system""s propeller can be selectively raised and lowered to fix its depth in the water and can be independently adjusted in its angle of orientation to establish an optimum set of propulsion conditions such as for speed and efficiency of operation.